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RTD Application

Mateus
Prodigy 110 points

Other Parts Discussed in Thread: ADS1248, LMP90100

Hello,

    I'm designing a RTD solution with 2, 3 and 4-wire support at the same board. LMP90100 seems to be a good option. ADS1248 is also an option, but the 50/60 Hz rejection is not so improved (< 100 dB). I have two questions:

First: In the "LMP90100 Evaluation Board with Sensor AFE Software User’s Guide" document, wire configuration jumpers explanation are correct ? ( JP11 )  As in 4-wire, I think "except P7-8" is correct and not J9-10 (IB2). Other question, in 2-wire configuration, VIN6_VREFP is used only as reference or also as VIN.

Second: How bad is using MUX or analog switches for 2, 3 and 4-wire implementation ? My idea is that an input port can be used with 2, 3 or 4-wire RTD and I dont wanna use jumpers. 

  • 0
    TI__Intellectual 1635 points

    Hi Mateus,

    Regarding the user's guide >> the picture I'm showing below is figure 14 in the LMP90100EB User's Guide.  It shows the LMP90100 evaluation board jumper configuration for a 3-wire RTD.  These jumpers configuration are correct. 

    If you are asking for a 4-wire RTD configuration, then you will need to connect a 4-wire RTD to J10 (the picture below only shows 3 wires), and you need to jumper pins 5 & 6 (of JP11) as well.

     

    In a 2-wire configuration, you will probably need to use the VIN6_VREFP2 both as an input pin and as VREF2.

    You can use an external MUX or analog switches (instead of jumper) for your 2, 3, and 4-wire RTD implementation.  I'm not sure what you mean by "bad", but this configuration will be more constly because you have to include this external MUX, and you will have to code your uC to control the MUX. 

     

  • 0 in reply to AmyLe
    Prodigy 110 points

    Hi Amy,

       Thanks a lot. I have more questions about HW implementation. So, I send you an e-mail. Could you take a look ?

    Best regards,

    Mateus.